Patent GB-964984-A (GB)
Title: Abrasive articles and the manufacture thereof
IPC: C08L61/10
Filed: 1961-08-24
Abstract: A method of making coated abrasive grains comprises heating abrasive grains, mixing them with a single-stage liquid phenol-aldehyde resin, heating the mixture until the grains are coated with the resin and the resin contains 15% by weight or less of materials having boiling-points below the vaporization temperature of the cured resin, and coating the grains with a dry two-stage heat-hardenable phenol-aldehyde resin mixed with a formaldehyde donor. Specified abrasive grains are fused alumina, boron carbide, silicon carbide, flint, corundum, garnet, sand and emery.  Fillers, e.g. cryolite, lime, asbestos, magnesium oxide or barytes may be mixed with the two-stage resin prior to use. Examples are given.ALSO:A method of making abrasive grains for the production of abrasive articles comprises heating abrasive grains, removing them with a single-stage liquid phenol-aldehyde resin, heating the mixture until the grains are coated with the resin and the resin contains 15% by weight or less of materials having boiling points below the vaporisation temperature of the cured resin, and coating the grains with a dry two-stage heat-hardenable phenol-aldehyde resin mixed with a formaldehyde donor.  The coated abrasive grains are cold-pressed into the desired shape and heated to cure the resins.  Specified abrasive grains are fused alumina, boron carbide, silicon carbide, corundum, flint, gamet, sand and emery.  Fillers, e.g. cryolite, lime, asbestos, magnesium oxide or barytes may be mixed with the two-stage resin prior to its admixture with the coated grains. Tackifiers, e.g. furfural, furfuryl alcohol or tricresyl phosphate may be added to the grains prior to moulding. Specified water soluble resins are phenol-formaldehyde resins.  Specified two-stage resins are phenol-formaldehyde resins and the specified formaldehyde donor is hexamethylene tetramine. Examples are given.ALSO:Abrasive articles are made by heating abrasive grains, mixing them with a single-stage liquid phenol-aldehyde resin, heating the mixture until the grains are coated with the resin and the resin contains 15% by weight or less of materials having boiling points below the vaporization temperature of the cured resin, coating the grains with a dry two-stage heat-hardenable phenol-aldehyde resin mixed with a formaldehyde donor, cold pressing the coated grains to the desired shape and heating to cure the resins.  Specified abrasive grains are fused alumina, boron carbide, silicon carbide, corundum, flint, garnet, sand and emery. Fillers, e.g. cryolite, lime, asbestos, magnesium oxide or barytes may be mixed with the two-stage resin prior to its admixture with the coated grains. Examples are given.ALSO:A method of making coated abrasive grains comprises heating abrasive grains, mixing them with a single-stage liquid phenolaldehyde resin, heating the mixture until the grains are coated with the resin and the resin contains 15% by weight or less of materials having boiling points below the vaporization temperature of the cured resin, and coating the grains with a dry two-stage heat-hardenable phenol-aldehyde resin mixed with a formaldehyde donor.  Specified abrasive grains are fused alumina, boron carbide, silicon carbide, flint, corundum, garnet, sand and emery.  Fillers, e.g. cryolite, lime, asbestos, magnesium oxide or barytes may be mixed with the two-stage resin prior to use. Examples are given.